Shetland Isles SMR

This section summarises the information from the Marine Protected Areas (MPAs) and intertidal and continental shelf habitats assessments from SMA2020. It also provides information from the relevant case studies relating to Priority Marine Features (PMFs), with a focus on habitats.  Further work is required to enable assessment at a regional scale for most species; this will be included in Scotland’s next marine assessment.

At a regional scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018.  For the marine habitats, the focus is on interpreting the relevant intertidal and continental shelf habitat assessments – biogenic habitats, predicted extent of physical disturbance to the seafloor  (BH3) and intertidal seagrass beds.  For PMFs, a summary is provided of the changes in our understanding of the habitats of most relevance to the Sheltand Isles SMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are 25 MPAs in the Shetland Isles SMR that contribute to the Scottish MPA network (see Table 1).  Some of these MPAs overlap completely or partially in terms of their spatial coverage and/or the features (habitats, species, etc.) they were set up to help conserve.  They are counted as separate MPAs because they have been established under different legislation which influences the way in which they are managed.  Also note that there are MPAs that straddle the boundaries between different SMRs/OMRs.  Where this is the case, these MPAs have been counted as contributing to the MPA network in all of the SMRs/OMRs in which they are present.  This means that the total number of MPAs in Scotland cannot be calculated through combining the SMRs/OMRs totals.  Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole.  

Table 1. Numbers of types of MPAs in the Shetland Isles SMR that contribute to the Scottish MPA network, including number of new MPAs introduced since 2012.

Note that in December 2020 there were another three SPAs designated in this SMR in addition to those in the table above (i.e. Bluemull and Colgrave Sounds, East Mainland Coast, Shetland and Seas off Foula).

Highlights from the various MPAs include:

The MPAs in Shetland Isles SMR cover a wide range of natural heritage features including birds, marine mammals, fish, benthic and intertidal habitats, and geomorphological features, as well as the only Demonstration and Research MPA in Scotland – Fair Isle.  The high energy environment and spectacularly clear waters of Fetlar to Haroldswick MPA are the perfect combination for maerl beds, kelp and seaweed communities, shallow tide-swept sands with burrowing bivalves, and horse mussel beds to thrive. Birds from one of Scotland’s largest colonies of breeding black guillemots (> 2000 individuals) forage over these rich seabed habitats.  The Mousa to Boddam MPA contains the most consistent and reliable sandeel recruitment areas in the SMR.  The sandeel populations (and fishery) here are dependent upon an influx of young fish (less than one year old) from a large spawning area situated to the west and north of Orkney.  Mousa SAC, off the east coast of Shetland Mainland, supports one of the largest groups of harbour seal in the SMR; the large rocky tidal pools on the island are of particular importance, as they are frequently used by the seals for pupping, breeding and moulting.  The SAC is also designated for its reefs and submerged or partially submerged sea caves.  The Vadills SAC, at the head of Brindister Voe is an outstanding example of a complex lagoon system supporting a wide range of communities with a high diversity of species. It comprises a number of shallow basins and has examples of both lagoonal inlets and silled lagoons. This extremely sheltered, undisturbed and natural environment has a gradation of habitats from brackish to fully marine conditions, with still too fast-flowing water, and soft, flocculent, peaty-mud through coarse sediments including maerl to bedrock and boulders.  The Shetland Isles SMR is important for its populations of breeding seabirds and wintering waterbirds, and has a large number of SPAs, including Foula SPA which is important for a wide range of breeding seabirds and is one of only seven known nesting localities in the EU for Leach’s petrel. Both the Mousa to Boddam MPA and the Fetlar to Haroldswick MPA sit within the Shetland carbonate production area, a key geodiversity area in Scottish waters. The Shetland carbonate production area is an internationally important example of a non-tropical shelf carbonate system. These sediments supply the carbonate sands to the coastal machair around Shetland which supports specific and diverse grassland vegetation and is one of the rarest habitats in Europe.

Progress in managing MPAs

The progress in implementing management for MPAs in the Shetland Isles SMR is summarised in Table 2.  This includes information on where spatial management measures are in place and where they are under discussion.  It also includes information on the number of MPAs that have been monitored, whether by statutory bodies or through citizen science.

Table 2. Summary of progress in managing Marine Protected Areas in the Shetland Isles SMR. Note that the spatial measures listed in the table are in addition to the protection provided as a result of consideration of activities/developments through licensing and consenting processes. Also, the monitoring of mammals and habitats within SSSIs and SACs has been split out to reflect the different programmes of work.  These figures cannot be added together to provide a total number of SSSIs and SACs in which monitoring took place because of overlaps in coverage.  

Within the Shetland Isles SMR there are currently no specific fishing orders or Marine Conservation Orders in place for MPAs. However, the Shetland Shellfish Management Organisation has put restrictions on scallop dredging in certain parts of Fetlar to Haroldswick MPA, Sullom Voe SAC and The Vadills SAC to protect sensitive habitats including  maerl beds and horse mussels.  Further management measures  of various fishing activities are under discussion for Fetlar to Haroldswick MPA, Mousa to Boddam MPA, Mousa SAC, Papa Stour SAC and Sullom Voe SAC.

During this assessment period the majority of the MPAs have been monitored at least once by the statutory bodies, and some have had multiple visits.  Monitoring has covered seabirds, subtidal habitats, otters and seals.  Seal monitoring continues to be undertaken via a collaboration between the Sea Mammal Research Unit, NatureScot and other partners.

Information on MPA boundaries can be viewed in Marine Scotland’s NMPi. To find out more about specific MPAs, please visit NatureScot’s SiteLINK.  Detailed reports on habitat monitoring are referenced in Further reading – seabed habitat monitoring reports.

Intertidal and continental shelf habitats

SMA2020 contains three relevant habitat assessments: intertidal seagrass beds, subtidal biogenic habitats, and predicted extent of physical disturbance to seafloor.  Assessment of the status of subtidal biogenic habitats is based on temporal reductions in extent of six habitat types: seagrass beds, serpulid aggregations, flame shell beds, maerl beds and horse and blue mussel beds.  Although beds of subtidal seagrass, maerl, blue mussels and horse mussels have been recorded within the region, no data are available on temporal changes in extent of these habitats and hence no status assessments could be made.  There are no records of flame shell beds or serpulid reefs.  There is only a single record of an intertidal seagrass bed in the region, so no status assessment of the habitat could be completed for SMA2020, as this is dependent upon the availability of time series data.  Modelling work was carried out as part of the assessment to predict the extent of physical disturbance to the seafloor more generally.

Predicted physical disturbance to the seafloor

To assess physical disturbance to seafloor habitats SMA2020 employed a modelling approach which generates a map of predicted relative disturbance levels from demersal fishing activity on a scale of 0 (zero) to 9 (severe).  The map was produced by the combination of information on the distribution of habitats, the sensitivity of the habitats (and species present to varying degrees) and the fishing pressure from demersal trawling, dredging and seine netting.  Fishing pressure information was derived from Vessel Monitoring System (VMS) data from 2012 - 2016 and was categorised as either surface abrasion (disturbance of surface and upper layers of sediment) or sub-surface abrasion (disturbance to a depth of >3 cm).  The final predicted disturbance index utilises the greater of these two pressure values and for descriptive purposes has been categorised as no disturbance (0), low disturbance (1-4) and high disturbance (5-9).

It should be emphasised that this method does not measure disturbance to seabed habitats, but predicts relative levels of disturbance. These relative levels are dependent upon the accuracy of habitat data and sensitivity assessments.  Many of the habitat data are derived from modelling and there is a low level of confidence in its accuracy.  Geographical variation in the accuracy of the sensitivity information employed is likely to be great, being dependent upon the level and quality of information used locally.  A significant limitation of the method is that during the assessment period pressure data were only available for vessels >12 m, which has probably resulted in an underestimation of disturbance.

Predicted habitat disturbance by mobile demersal fishing for the Shetland Isles SMR is the highest for all SMRs in terms of the proportion of the seabed with 80% high disturbance compared to an average of 50% and at 4% has the smallest proportion of the seabed predicted to experience no disturbance (average of 12% for all SMRs) (Figure 3).  High disturbance levels occur particularly around the north of the archipelago and to the south west and south, where the sea bed is dominated by coarse sediments.  These predicted levels closely correspond to the sensitivity of the habitat to surface abrasion, as well as the surface fishing pressure.

Figure 3.  Predicted physical disturbance to the sea floor in the Shetland Isles SMR and proposed prohibition areas for all mobile demersal fishing.  Also shown are Shetland Shellfish Management Organisation (SSMO) scallop dredging exclusion areas.

Priority Marine Features and birds (non-PMF)

Overview of recorded PMFs and birds

The Shetland Isles SMR supports a range of PMFs and breeding seabirds as well as wintering waterbirds (i.e. waders, estuarine waterfowl, seaduck and coastal water feeding birds) as detailed in Table 3. 

Table 3: Details of PMFs, seabirds, and wintering waterbirds found in the Shetland Isles SMR

The Shetland Isles SMR supports 50 PMF habitats and species and 35 marine bird species.

Subtidal blue mussel beds are restricted to a few scattered locations in Scotland, including within Whiteness Voe, whilst the most northerly record of a horse mussel bed in Scotland is in Bluemull Sound.  Sandeels are present in the SMR and provide an important food source for many commercial fish species. The sandeels around Shetland comprise both locally spawned fish and ones that spawned north west of Orkney and were carried into the SMR by the ocean currents.  Of the 15 species of cetaceans found in the Shetland Isles SMR, five are considered year-round residents (killer whale, minke whale, white-beaked dolphin, harbour porpoise, and Risso’s dolphin), while the others are either seasonal visitors or occasional deep-water visitors.  There are also important populations of both grey and harbour seals and otters.  Shetland Isles SMR is home to internationally important colonies of breeding seabirds, including the colonies at Hermaness, Noss, Sumburgh Head and Fair Isle and is a breeding stronghold for Arctic skua.

Progress in understanding of intertidal and continental shelf habitats listed as PMFs

Over the last 10 years there has been a change in emphasis of survey work in the SMR. Much of the earlier work focused on obtaining an understanding of the distribution and conservation importance of habitats and species, and monitoring the environmental impact of the Sullom Voe oil terminal. Latterly survey effort has become increasingly associated with the establishment and monitoring of the Mousa, Papa Stour and Sullom Voe SACs.  Over the 2012 - 2018 assessment period the focus has also turned to improving understanding of the wider distribution of PMFs.

The temporal sequence of records of all PMF habitats is provided in Table 4, based on inclusion in the Marine Recorder (2021) and GeMS (2021) databases, as well as identified additional sources.  Associated commentary, however, is restricted to PMFs for which the information has the potential to inform regional marine planning.  For example, some PMFs are excluded on the basis that they are very widely distributed and for which the records represent a small proportion of their likely distribution, such as several of the kelp habitats.  The distribution of records of these selected PMFs is illustrated in Figure 4.

Table 4.  Temporal frequency of PMF habitat records within the Shetland Isles SMR obtained from GeMS (2021), Marine Recorder (2021) and other sources.  The numbers of All records are given, as well as those from Citizen Science (CS) surveys alone.

The relative inaccessibility of this SMR has no doubt been a factor in the low proportion of PMF records provided by citizen science surveys (2% before 2012 and 8% more recently).

There has been little or no improvement in recent years in the distributional knowledge of many of the PMFs listed in Table 4, with maerl beds a notable exception.  The few pre-2012 maerl bed records in the region have been greatly supplemented in recent years.  SNH surveys in 2012 (Hirst et al., 2013) and 2016 (Harries et al., 2017) investigated maerl distribution and condition from respectively Fetlar to Haroldswick and off Mousa, the latter including mapping of a 13-ha bed.  Rich live maerl was recorded in both areas (Figure 4).  A 2019 Marine Scotland video survey (Shucksmith, Shelmerdine, & Shucksmith, 2021) provided additional distributional detail for Fetlar to Haroldswick, Mousa and north of Papa, and confirmed the presence of beds in Yell Sound and Wadbister Voe.  The same survey also added new records for maerl or coarse shell gravel with burrowing sea cucumbers in the areas of Yell Sound and Fetlar to Haroldswick and tide-swept algal communities in the same localities, as well as north of Papa.

Survey work from 2012 onwards has also significantly improved knowledge of horse mussel bed distribution.  In particular, the 2012 SNH survey (Hirst et al., 2013) identified the widespread nature of the habitat in the Fetlar to Haroldswick area and the 2019 Marine Scotland survey (Shucksmith et al., 2021) provided further detail in this region and identified new beds in the Sullom Voe area and off Bressay.

A modest increase in the number of records of northern sea fan and sponge communities resulted from a 2017 Marine Scotland video survey in an area 10 km north east of Bressay (Moore, 2020).  The observations, however, indicate the presence of only low-diversity examples of the habitat.

Figure 4.  Temporal pattern of records of selected PMF habitats for the Shetland Isles SMR.

Status and trend in grey and harbour seals

There are no major grey seal breeding sites in Shetland Isles SMR which supports a relatively small population for which there has been little or no change and their status is assessed as ‘few or no concerns’.  The harbour seal population which was relatively stable from the early 1990s to the mid 2000s suffered a decline of around 40% in the mid 2000s and has subsequently shown little or no change since then and their status is assessed as ‘some concerns’.